A power inductor is mainly provided in a power circuit such as a DC-DC converter within a portable device. The power inductor is increasing in use instead of an existing wire wound choke coil as the power circuit is switched at a high frequency and miniaturized. Also, the power inductor is being developed in the manner of miniaturization, high current, low resistance, and the like as the portable device is reduced in size and multi-functionalized.
The power inductor according to the related art is manufactured in a shape in which a plurality of ferrites or ceramic sheets mode of a dielectric having a low dielectric constant are laminated. Here, a coil pattern is formed on each of the ceramic sheets, and thus, the coil pattern formed on each of the ceramic sheets is connected to the ceramic sheet by a conductive via, and the coil patterns overlap each other in a vertical direction in which the sheets are laminated. Also, in the related art, the body in which the ceramic sheets are laminated may be generally manufactured by using a magnetic material composed of a four element system of nickel (Ni), zinc (Zn), copper (Cu), and iron (Fe).
However, the magnetic material has a relatively low saturation magnetization value when compared to that of the metal material, and thus, the magnetic material may not realize high current properties that are required for the recent portable devices. As a result, since the body constituting the power inductor is manufactured by using metal powder, the power inductor may relatively increase in saturation magnetization value when compared to the body manufactured by using the magnetic material. However, if the body is manufactured by using the metal, an eddy current loss and a hysteresis loss of a high frequency wave may increase to cause serious damage of the material.
To reduce the loss of the material, a structure in which the metal powder is insulated from each other by a polymer may be applied. That is, sheets in which the metal powder and the polymer are mixed with each other are laminated to manufacture the body of the power inductor. Also, a predetermined base material on which a coil pattern is formed is provided inside the body. That is, the coil pattern is formed on the predetermined base material, and a plurality of sheets are laminated and compressed on upper and lower sides of the coil pattern to manufacture the power inductor.
However, there is a problem in which the power inductor manufactured by using the metal powder and the polymer is reduced in inductance due to an increase of a temperature. That is, the power inductor may increase in temperature by generation of heat of the portable device to which the power inductor is applied, and thus, the metal power forming the body of the power inductor may be heated to cause the problem in which the inductance is reduced. Also, the coil pattern and the metal powder within the body may contact each other in the body. Here, in order to preventing this phenomenon from occurring, the coil pattern and the body have to be insulated from each other.
Also, a base material on which the coil pattern is formed uses a material having magnetic permeability such as copper clad lamination CCL, and thus, the power inductor using the above-described base material may be reduced in magnetic permeability.